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Title: Science Case Reference: MUSE-MEM-SCI-052 Issue: 1.3 Date: 04/02/2004 Page: 97/100 8. Competitiveness 8.1. Introduction MUSE, as any second generation VLT instrument, should be able to maintain and expand the VLT world-wide competitiveness in 2010+. As such, it should not only be superior to existing instruments in terms of performance, but should also extend the scientific capabilities of the observatory into unique areas. In this section we try to assess its competitiveness. Competitiveness is generally a difficult issue to discuss, and even more difficult to properly quantify. The most valid approach is to compare MUSE with other instruments or facilities in view of each of the science goals, such as the comparisons already made and discussed throughout the various science case presentations. The key points to emphasize from these comparisons are that the MUSE sensitivity performance is around two orders of magnitude better than narrow-band imaging; the volume-depth which can be surveyed with MUSE is unprecedented; and its ability to provide both high-spatial resolution spectroscopic information across a wide field of view, or to get diffraction-limited resolution at visible wavelengths over a smaller area, are unparalleled by any other instrument, existing or planned. The MUSE science team believes that the large majority of the presented science cases are unique to MUSE, either because they are simply not feasible with other instruments (e.g. detection of high-z faint Ly α emitters that are not detectable in broad band imaging, even with HST), or because it would take in excess of 10–100 times longer to perform the same survey with other facilities, and so are simply not tenable. For example, as discussed in section 4.4, the combination of large field-of-view with seeing-limited spatial sampling makes MUSE WFM an unrivalled tool for background-limited spectroscopy of resolved stellar populations in nearby galaxies: 260× more efficient than FLAMES, and 210× more efficient than the GMOS-IFU. It is also possible to compare MUSE with other instruments in term of generic performance. This approach is also important, not only because in seven years, science goals may have evolved, but also because the science team has its own bias and cannot represent all interests of the entire ESO community. MUSE is an IFU and should therefore be compared to others IFUs that share some of its characteristics: wide-field of view, high spatial resolution, large simultaneous spectral range and medium spectral resolution. Here we compare the two modes of MUSE with existing or planned wide-field or high spatial resolution IFUs.
Title: Science Case Reference: MUSE-MEM-SCI-052 Issue: 1.3 Date: 04/02/2004 Page: 98/100 8.2. Wide field IFU Among the very few existing wide-field IFUs that could compete with MUSE, VIMOS has the largest field of view with 0.8 arcmin². This large field of view, however, is only obtained at R~250: a spectral resolution far too low to be competitive for line emission detection and analysis, or for accurate sky-subtraction in the near-infrared. We have therefore restricted the comparison to the high spectral resolution mode of VIMOS. To quantify the performance comparison between the two instruments, we present in the following table some possible figures of merit. We have also included SAURON, another wide field IFU operating at the WHT, as a reference in this table. SAURON VIMOS MUSE MUSE/VIMOS LR mode HR-Blue WFM Telescope area (m²) 13.1 51.7 51.7 1.0 Ω (arcsec²) 41x33 27x27 60x60 4.9 Grasp (m².arcsec²) 17724 37689 186120 4.9 Throughput 0.2 0.066 0.24 3.6 Etendue 3545 2487 33502 17.6 Resolving power 1200 2500 3000 1.2 Nb of resolved spectral elts 129 920 2048 2.3 Spectral power (x 10 6 ) 0.16 2.3 6.1 2.6 Nb of resolved spatial elts 1,431 1,600 40,000 13.5 Spatial power (x 10 6 ) 1.9 1.2 144.0 120.0 3D power (x 10 12 ) 0.3 2.8 878.4 312.0 Table 8-1: Comparison of wide field IFUS Note on the table parameters • Grasp is the field of view times the telescope area • Etendue is the field of view times the throughput • Spectral power is the number of resolved spectral elements times the spectral resolution • Spatial power is the number of resolved spatial elements times the field of view. In the case of MUSE, a spatial resolution of 0.3 arcsec is assumed. In the case of VIMOS, this is simply the number of spaxels. • 3D power is the product of spatial and spectral power One interesting number is the Etendue, which is directly linked to the speed for performing a survey. Because of its large field of view and better throughput, MUSE is more than ten times faster than VIMOS. Another key number is the 3D power, a number that measures the datacube information content that could be explored by the instrument. In this respect, MUSE is more than 2 orders of magnitude better than VIMOS. These figures of merit are just an indicator to facilitate a quantifiable comparison. The capability of an instrument to conduct very faint-object science depends on a number of
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The median descendant mass of galax
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with the slicer development for NIR
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Science Case Coordinator : R. Bacon
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Title: Science Case Reference: MUSE
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Keck Telescope (Rhoads et al. 2000)
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